The design of an effective user interface poses many challenges. One challenge is how to provide a user with an optimal amount of visual information or functionality, given the space limitations of a display and the needs of a particular user. This challenge can be especially acute for devices with small displays, such as smartphones or other mobile computing devices. This is because there is often more information available to a user performing a particular activity (e.g., browsing for audio or video files in a library of files) than can fit on the display. A user can easily become lost unless careful attention is paid to how information is presented on the limited amount of available display space. Visual cues are useful for indicating, for example, a user's location when browsing a list or other collection of data, since it is often not possible to show an entire collection (e.g., a list of contacts stored in a smartphone) on a small display.
Whatever the benefits of previous techniques, they do not have the advantages of the techniques and tools presented below.